Process of cleaning piping systems



United States Patent 3,523,826 PROCESS OF CLEANING PIPING SYSTEMS Kenneth J. Lissant, St. Louis, Mo., assignor to Petrolite Corporation, Wilmington, Del., a corporation of Delaware N0 Drawing. Filed July 17, 1967, Ser. No. 653,627 Int. Cl. B08b 9/06; (123g /00 U.S. Cl. 134-22 8 Claims ABSTRACT OF THE DISCLOSURE A process for cleaning piping systems, particularly those systems containing particulate matter, which is characterized by circulating a thixotropic or pseudo-plastic fluid having non-Newton viscosity properties for a time sufficient to effect such cleaning. An excellent pseudoplastic fluid is a stable, viscous, thixotropic high internal phase emulsion, where the internal phase is the major part of the emulsion, for example, containing at least about 60% internal phase, such as about 80%, but preferably at least about 90% by volume. Auxiliary additives may also be added to the emulsion. After cleaning, any residual emulsion may -be removed by flushing the system with a fluid which is miscible with the emulsions external phase or which is capable of breaking the emulsion.

In many areas of industry when new equipment is being readied for operation, it is necessary to be sure that all particulate matter has been removed from piping systems such as hydraulic control lines, cooling circuits and lubrication lines. Present day conventional practice is to chemically clean these lines with acid and/or detergents, and then to pump water or a light oil through the system to flush out particulate matter. The mechanism by which particulate matter is removed from the system is purely a process of mechanical transport by virtue of the velocity of the fluid being pumped. Conventional flushing fluids, Whether water or oil, are Newtonian liquids; that is, their viscosity is not a function of the rate of flow. Occasionally Newtonian fluids of increased viscosity have been used for flushing purposes. However, since the viscosity is constant with respect to rate of flow, they require excessive energy to drive the pumps, and they are diflicult to flush from the systems.

-I have now devised a method for cleaning piping systerm which is characterized by circulating a pseudo-plastic or thixotropic fluid exhibiting non-Newtonian viscosity properties in the system for a time suflicient to effect cleaning. By non-Newtonian, I mean a fluid of thixotropic or pseudo-plastic character. By definition, these fluids pos sess the property of exhibiting variable apparent viscosity when the shear rate is varied. Stated another way, when these fluids are pumped at low shear rates, they behave as though they are extremely viscous fluids; but as the pumping rate is increased and concomitantly the shear rate increases, the fluids appear to shear thin and then behave as though they have low viscosities. 'I have found that fluids of such a character, when flowing through small pipes at normal pumping velocities, exhibit a low enough effective viscosity to entrain particulate matter and to at the same time afford easy pumping characteristics. However, the same fluids, upon entering a portion of the piping system of larger cross section where the lineal velocity is reduced, appear to increase in viscosity and therefore retain the particulate matter in suspension, instead of allowing it to settle as occurs in the case of Newtonian fluids.

3,523,826 Patented Aug. 11, 1970 For the purpose of this invention, any thixotropic or pseudo-plastic fluid with suitable pumping characteristics Which was compatible with the materials of construction of the system to be purged, could be advantageously employed. Among such fluids could be mentioned polymer solutions, gels and emulsions.

I have particularly found, however, that the employment of emulsions, and specifically high-internal-phaseratio emulsions, i.e. where the internal phase is a major part of the emulsion, are particularly well suited for this purpose; since they are more readily flushed from the system after purging and since they may be formulated with a variety of internal and external phases to achieve compatibility with the materials of construction. I have also found that from an economic standpoint, large volumes of emulsion may be formulated with inexpensive major constituents, thereby providing inexpensive fluids.

The emulsions employed in the process are high-internal-phase-ratio emulsions. These high-internal-phase-ratio emulsions are pseudo-plastic fluids; that is, rather than exhibiting Newtonian viscosity properties, the apparent viscosity of the formulation is a function of the rate of shear. Simply stated, these fluids behave like elastic solids when at rest or when subjected to forces below their yield point. Above their yield point they begin to flow, and at normal pumping velocities their viscosity is close to the viscosity of the external phase employed. I have found that such emulsions, when pumped through a contaminated system, entrain particulate matter and are extremely effective in removing such materials from the system. Not only are extremely fine particles entrained and removed, but large flakes of rust, mill scale, weld spatter, etc., are etficiently transported through the system. The efliciency of the process is further enhanced by the fact that high lineal velocities are not required for the suspension of particulate matter, since the apparent viscosity increases with a decrease in shear rates, thus preventing resettling of entrained particulate materials. Because these emulsions can be prepared with either an oil or a water-type external phase, they can be appropriately selected so as to be non-corrosive or non-contaminating to the particular system and can be quickly and efliciently flushed from the system by the use of fluids of the same type as the external phase. These emulsions contain an internal phase which is the major part of the emulsions; for example, at least about 60% such as at least about but preferably in excess of about by volume.

High internal phase emulsions which can be employed in this invention are those disclosed in the following patent applications:

Related Application and Other Serial No. Filed Title Comments 286,877 May 20, 1963 Stable Emulsions Now abandoned. 302,177 Aug. 14, 1963 Hybrid Fuels I Do. 411,103 Nov. 13, 1964 Ertnulsions Prepara- Do.

ion

541,738 Apr. 11, 1966 Method of Resolving Now U.S. Pat. No.

Thixotropic Jet and 3,328,418, granted of SN. 286,877 and now abandoned. 637,332 May 10, 1967 Essentially non-aqueous emulsions.

The thixotropic emulsions of this invention, which have the characteristics of a solid at rest and a liquid when force is exerted on it, have the following advantages:

(1) Nonadhesive: They do not tend to stick to the sides of the container or piping system.

(2) Viscosity: The apparent rest viscosity is greater than 1000 cps., generally in the range of 10,000100,000 or greater, preferably 50,000-100,000, cps. However, under low shear, they will flow with a viscosity approaching that of the liquid phases. On removal of shear, the recovery to original apparent rest viscosity is nearly instantaneous. The hysteresis loop is very small.

(3) Temperature stability: Increased temperature has little eifect on viscosity until the critical stability temperature is reached at which point the emulsion breaks into its liquid components. This permits a wide temperature range of operation.

(4) Shear stability: Emulsions may be subjected repeatedly to shear without degradation so long as the critical shear point is not reached. At this point the emulsion breaks. However, the critical shear point is sufficiently high to permit pumping at high rates.

(5 Quality control: With these emulsions it is easy to reproduce batches with identical properties due to the absence of any gel structure.

(6) Solids content: Emulsions will flow well even with high solids content since they have a broad range between rest viscosity and viscosity under modest shear.

In contrast to very high volume percent solid loading in gels or slurries which result in a putty, these emulsions can suspend such solids in the internal phase while allowing the external phase to govern flowability.

The above patent applications which are, by reference, incorporated into the present application relate to stable, viscous thixotropic emulsions and to the uses, preparation, etc., of these emulsions.

Whether an oil external or an aqueous external phase is employed in preparing these emulsions will depend on the particular system in which it is employed. For example, since water is less expensive than oily solvents, it can be used to make up the bulk of the emulsion while the oily external phase will contact the pipe surface thus reducing the corrosive effect of an aqueous system. To further reduce the possibility of corrosion, a corrosion inhibitor may be employed. In addition, where certain oil soluble contaminants are present in the pipe, the oil external phase will help remove these materials by dissolving them. On the other hand, where certain materials present are water soluble, it may be desirable to employ a water external emulsion in order to dissolve these materials.

Stated another way, besides physically sweeping the piping system, the emulsion may also act as a solvent for certain soluble contaminants present in the pipe.

In addition, where appropriate, the external phase may contain additives which may chemically react with the contaminants so as to facilitate removal. For example, the aqueous phase may consist of a solution of a mineral or organic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, sulfamic acid, citric acid, acetic acid, etc.

The aqueous phase may also consist of a solution of inorganic bases, organic bases or chelating agents, such as sodium hydroxide, ammonium hydroxide, ethylenediamine, mono, di or tri-ethanolamines, ethylenediaminetetra-acetic acid, etc. The aqueous phase may also contain water soluble organic materials such as alcohols, esters, etc., to modify its solvent properties. Further, the non-aqueous phase may contain aromatic or terpenic materials or alcohols, esters, etc. to modify its solvent properties.

Thus, the emulsions employed in this invention include:

(1) Oil-in-water emulsions (2) Water-in-oil emulsions (3) The above emulsions of 1) and (2) where water-like substances are employed in place of water as described in S.N. 637,332 filed May 10, 1967.

(4) The above emulsions where additives such as antifreeze compounds, corrosion inhibitors, biocides, etc. are employed in either or both phases as described in S.N. 565,702, filed July 18, 1966.

(5) A continuous method of preparing these emulsions, as described in S.N. 411,103, filed Nov. 13, 1964. Thus, any of the oily and non-oily materials, emulsifiers and techniques, etc. described in the above applications can be employed in preparing the emulsions of this invention.

Since theseemulsions have been described in such great detail in the above applications repetition herein is unnecessary.

The following examples are presented for purposes of illustration and not of limitation. Oxyalkylations were carried out by the general procedure described in US. Pat. 2,572,886, Example 1a, columns 9 and 10.

Emulsifier A An emulsifier was prepared by oxyalkylating 1,3-butanediol with 3.0 parts by weight of butylene oxide, 32.2 parts of propylene oxide and 16.6 parts of ethylene oxide in the order given.

An emulsifier was prepared by oxyalkylating triethyleneglycol with 5.1 parts by weight of butylene oxide, 30.0 parts of propylene oxide and 22 parts of ethylene oxide in the order given.

An emulsifier was prepared by oxyalkylating octyl phenol with 0.69 part by weight of ethylene oxide.

The following example illustrates the preparation of a thixotropic water external-oil high internal phase emulsion.

EXAMPLE 1 Three quarts of water and ml. of Emulsifier A were thoroughly mixed. One gallon of kerosene was then added and mixed into this material until a smooth emulsion was formed. This premix was then placed into a 20 gallon open mixing vessel, equipped with an anchor type stirrer. With the stirrer revolving at about 200 r.p.m., additional kersosene was added until a total of ten gallons of kerosene had been mixed in. The result was a white, highly thixotropic, oil-in-water emulsion.

The following example illustrates the preparation of a thixotropic water external-oil high internal phase emulsion.

EXAMPLE 2 A two inch diameter, Viking pump, driven by an electric motor at 805 r.p.m., was equipped with an eight foot flexible hose on the outlet and a similar flexible hose on the inlet. The ends of the two hoses were placed in a 50 gallon, open head, steel drum. With this arrangement, material could be pumped out of the drum, through the pump, and back into the drum.

One gallon of water and one pint of Emulsifier B were mixed together and placed in the steel drum. While this material was circulated by the pump, mineral spirits was slowly added to the intake of the pump. In about 15 minutes, 50 gallons of mineral spirits had been added and the result was a thick, white, jelly-like emulsion.

The following example illustrates the preparation of an oil externalhigh internal water phase thixotropic emulsion.

EXAMPLE 3 A two inch diameter, Viking pump, driven by an electric motor at 850 rpm, was equipped with an eight foot flexible hose on the outlet and a similar flexible hose on the inlet. The ends of the two hoses were placed in a 50 gallon, open head, steel drum. With this arrangement, material could be pumped out of the drum, through the pump, and back into the drum.

One gallon of kerosene and one pint of emulsifier C were mixed together and placed in the steel drum. While this material was circulated by the pump, mineral spirits was slowly added to the intake of the pump. In about 15 minutes, 50 gallons of water had been added and the result was a thick, white, jelly-like emulsion.

The following examples are presented to illustrate the efficacy of these emulsions in cleaning piping systems.

Cleaning Example 1A A piping system containing a variety of pipe fittings, valves, and a pump had been purged by circulating kerosene through it for a period of several hours until a filter in the line no longer showed retention of particulate matter. It was then judged to be clean and ready for use. When an emulsion of the type described in Example 1 was then circulated through this system, sufiicient particulate matter was entrained and transported to the filter element to cause a serious rise in back pressure. The filter was then examined, and a substantial amount of additional particulate matter was found. Further tests disclosed that the emulsion had removed particulate matter from low spots in the system; and that by circulating emulsion through the system for less than one-half hour, all traces of particulate matter were then removed.

Cleaning Example 2A A test engine with accompanying fuel tanks, fuel control equipment, and piping had been operated on LIP-4 for a number of hours with no indication of particulate contamination. When this system was switched to an emulsion of the type described in Example 2, trouble was encountered with fuel nozzle plugging and sticking of the fuel control valve. Examination of the system disclosed the presence of particulate matter at these points. It was determined that this particulate matter was not contained in the emulsion supplied to the system, but that it had entrained particulate matter from portions of the system where the previous flushing with JP-4 could not remove them. Subsequent flushing of the system with additional emulsion resulted in complete removal of all particulate matter.

Cleaning Example 3A A piping system similar to Example 1A was cleaned employing the emulsion of Example 3.

Although the above emulsions are illustrated by hydrocarbon-in-water and water-in-hydrocarbon emulsions prepared with oxyalkylated emulsifiers, suitable emulsions can also be prepared, for example, from materials other than hydrocarbons and water-like materials other than water. Thus, emulsions can be prepared from oily halocarbons, oily organic esters, etc. or a non-oily aqueous solutions, such as of acids, bases, alcohols, etc. or of non-oily water type, non-aqueous solvents, such as for example dimethyl formamide, etc. Although oxyalkylated emulsifiers are employed in the above examples other emulsifiers capable of forming such emulsions can also be employed, for example, the acylated reaction product of morpholine,

NH: CHzCHzN aCHzCHzOH and oleic acid, etc. These emulsions can be continuously prepared by the method described in S.N. 411,103.

In addition, suitable thixotropic or pseudo-plastic materials other than emulsions which exhibit non-Newtonian viscosities may also be employed.

As is quite evident, a wide variety of thixotropic emulsions are useful in this invention. It is, therefore, not only impossible to attempt a comprehensive catalogue of such compositions, but to attempt to describe the invention in its broadest aspects in terms of specific chemical names for the components of such emulsions would be too voluminous and unnecessary since one skilled in the art could by following the description of the invention herein prepare an appropriate emulsion. This invention encompasses the use of thixotropic emulsions in cleaning piping systems and the individual components of such emulsions are important only in the sense that they effect this function. To precisely define each specific useful phase of the emulsion and emulsifier in light of the present disclosure would merely call for chemical knowledge within the skill of the art in a manner analogous to a mechanical engineer who prescribes in the construction of a machine the proper materials and the proper dimensions thereof. From the description in this specification and with the knowledge of a chemist, one will know or deduce with confidence the applicability of specific phases of the emulsions and emulsifiers suitable for this invention by applying them in the process set forth herein. In analogy to the case of a machine, wherein the use of certain materials of construction or dimensions of parts would lead to no practical useful result, various materials will be rejected as inapplicable where others would be operative. I can obviously assume that no one will wish to use a useless emulsion nor will be misled because it is possible to rnisapply the teachings of the present disclosure to do so. Thus, any thixotropic emulsion that can perform the function stated herein can be employed. Analogously other thixotropic or pseudo-plastic fluids besides emulsions must also be emphasized.

The term piping systems as employed herein relates to fluid transport systems including but not limited to pipes, integral fluid channels, ducts, weirs, industrial equipment containing fluid transport circuits, motors, turbines, etc., and associated tanks, reservoirs, pumps and hydraulic mechanisms, etc.

Having thus described my invention what -I claim as new and desire to obtain by Letters Patent is:

*1. A process for cleaning a piping system which is characterized by circulating in and through said system a thixotropic emulsion having a high volume ratio of internal phase to external phase, the emulsion having an emulsifying agent, an emulsifiable oil and a non-oil, the emulsion being an oil-in-non-oil or a non-oil-in-oil emulsion, the internal phase of said emulsion being present in said emulsion in an amount of at least by volume of the emulsion, said emulsion having the characteristics of a solid when at rest and the characteristics of a liquid when a force is exerted on it, said emulsion tending to be nonadhesive, said emulsion having a critical shear point sufiicient to permit pumping at high rates, and said emulsion having an apparent rest viscosity greater than about 1000 cps.

2. The process of claim 1 wherein the emulsion contains an auxiliary additive.

3. The process of claim 1 wherein, after circulating, the emulsion is flushed out of the piping system by a fluid miscible with the external phase of the emulsion.

4. The process of claim 1 wherein the emulsion is an oil-in-non-oil emulsion.

5. The process of claim 1 wherein the emulsion is a water-in-oil emulsion.

6. The process of claim 5 wherein the oil is a hydrocarbon.

7. The process of claim 1 wherein the emulsion is an oil-in-water emulsion.

carbon.

7 8 8. The process of claim 7 wherein the oil is a hydro- 2,810,665 10/1957 Szayna M; 134-22 XR 3,085,918 4/1963 Sherliker et a1. 134-40 XR References Cited 3,118,793 1/1964 Maloney et a1. 13441 XR UNITED STATES PATENTS 3,391,08 7/1968 YOfk 13440 XR 2/1936 Johnson 134-40 XR 5 MORRIS o. WOLK, Primary Examiner 8/1943 Coleman. 2/1944 ,Dobson et J. T. ZATARGA, Assistant Examiner 9/1949 Daugherty et a1. 134-22 p 10/1950 Pabstet a1. 10 134 40 5/1956 Nicholson et a1. 13440 XR 5/1956 De Lew et a1. 13440 XR 

